Currently I'm playing around with a little language called Io that...
well, it's not exactly "syntax-extending" so much as
"syntax-agnostic". :-) I'm simply smitten by the staggering variety of
syntax primitives which are being built right now in the push to v1.0 of
the language. They're talking about variations on switch/cond/select
statements right now and every day there's a dozen different variations
on the syntax while people play with them. All of them written in Io --
not even in a macro system, but in Io proper.
